Self check-out is great if, say, you’ve got one of those supermarkets where the teenaged clerks hate you for choosing their lane and spend more time talking to each other than scanning your items. It’s not so great if you force all of your customers to use the system because you’ve decided to close down every other human-powered lane but one.

If you’re one of those really smart coupon hoarders, you know to save up for double-coupon offers, because then you can get things for next-to-nothing. Nicole has used this strategy at Kmart in the past without problems, but this time she ran into an assistant manager who refused to honor the promotion, saying, “It’s not our policy. It’s not written down, but that’s the policy.”